1. Field of the Invention
The present invention relates to refrigerated display cabinets and more particularly, to an electrically heated glazed door structure for use in such cabinets.
2. The Prior Art
In U.S. Pat. No. 3,724,129 to Stromquist, the use of an optically transparent electrically conductive coating for preventing moisture condensation on the frontmost glazed surface of a refrigerated cabinet door is described. Such coatings, normally applied to the unexposed surface of the frontmost glass pane are in current wide use. This heating technique performs well where the ambient air has a relative humidity which is not excessive.
When such refrigerated cabinets are used in highly humid environments, it is found that even though the frontmost pane remains frost-free, the innermost pane (the pane which has been exposed to the interior environment of the cabinet) has a tendency to collect condensation while the door is open. The condensation turns to frost when the refrigerated cabinet door is closed, thereby substantially impairing the door's ability to attractively display products stored in the cabinet until such time as the door recovers its frost free condition.
Consumer shopping habits may further aggravate the situation. It is found that consumers in some areas tend to hold refrigerated cabinet doors open longer than do the consumers in others. This pattern of consumer behavior results in the innermost pane being exposed for a significant percentage of the time to the more highly humid ambient air, thereby aggravating the condensation problem, increasing the frost-free recovery time, and detracting from the utility of closed refrigerated cabinets.